TM 5-3805-281-24-1
Theory of Operation
NOTE: For operation of the front and rear pump
of servo piston pushes the piston down increasing
control valves, see Pump Control Valve
pump displacement (flow). The servo piston is
Operation in this group.
transmitted to the remote control sleeve (6) and load
sleeve (9) by the feedback link (15). The sleeves move
left until the path to return is closed. The oil at the
INCREASING FLOW (DISPLACEMENT)
large end of servo piston is now trapped holding the
pump at maximum displacement (flow rate) that is
When a function is actuated, the reduced pilot oil (28)
proportional to the pressure of the pump control valve
control signal from the pump control valve (3) to the
control signal.
piston (7) increases. The control signal pushes the
piston and remote control spool (5) to the left against
DECREASING FLOW (DISPLACEMENT)
the spring until the spring force and control signal
pressure are equal. Movement of spool opens a path
As the function is returned towards neutral, the
from the large end of servo piston to return in the
reduced pilot oil (28) control signal sensed at the
pump housing (14). Pilot oil on the small end of servo
piston (7) also decreases. The spring pushes the
piston pushes the piston down increasing pump angle
remote control spool and piston to the right. Movement
which increases the displacement (flow). The servo
of the spool opens a path for pilot oil (27) to flow to the
piston movement is transmitted to the remote control
servo piston large end (4). The pilot oil pressure
sleeve (6) and load sleeve (9) by the feedback link
applied to the servo piston large end pushes the piston
(15). The sleeves move left until the path to return is
up against the pressure applied to the small end
closed. The oil at the large end of servo piston is now
decreasing pump flow. The piston and remote control
trapped holding the pump at the displacement (flow
spool continues to be pushed to the right until spring
rate) that is proportional to the pressure of the pump
force again equals the reduced pilot oil control
control valve control signal.
pressure or until the spool contacts the piston (7)
cylinder when function is returned to neutral. As the
MAXIMUM FLOW (DISPLACEMENT)
pump displacement decreases, the movement is
transmitted to the remote control sleeve (6) and load
When the pilot controller lever is actuated to full stroke,
9025
sleeve (9) by the feedback link (15). The sleeves move
the reduced pilot oil (28) control signal from the pump
05
right until the path for pilot oil is closed. The oil at the
control valve (3) to the piston (7) increases to its
22
large end of servo piston is now trapped holding the
maximum. The control signal pushes the piston and
pump at the displacement (flow rate) that is
remote control spool to the left until the spool contacts
proportional to the pressure of the pump control valve
the maximum flow adjusting screw. Movement of spool
control signal.
opens a path from the large end of servo piston to
return in pump housing (14). Pilot oil on the small end
CED,TX08227,3093
1918APR982/2
6-22
